Dataflow and comparisons to true/false

[wmdietl]

Found another interesting example:

import org.checkerframework.checker.nullness.qual.Nullable;

class Bug {
  void foo(@Nullable Object obj) {
    if ((obj != null) == false) {
      // :: (dereference.of.nullable)
      obj.toString(); // BUG: no warning about this dereference
    }
  }
  
  void bar(@Nullable Object obj) {
    if (!(obj == null) == false) {
      // :: (dereference.of.nullable)
      obj.toString(); // BUG: no warning about this dereference
    }
  }
  
  void baz(@Nullable Object obj) {
    if ((obj == null) == true) {
      // :: (dereference.of.nullable)
      obj.toString();
    }
  }
}

Demo

Originally posted by @jdmota in #3267 (comment)